Rise in carbon dioxide unleashing global greening, faster food production, reforestation and new vegetation across the planet
by: Julie Wilson
A new study shows that Earth's vegetated lands or surfaces covered in plant life have greened "significantly" over the last 35 years. Using computerized models, scientists theorize that this so-called greening effect is in response to an increase in atmospheric carbon dioxide, as well as other, less influential contributors.
Published in the journal Nature Climate Change on April 25, the research concludes that about 25 to 50 percent of Earth's plant life has experienced a greening effect, increasing the leaves on plants and trees in an area equivalent to two times the continental U.S.
The amount of leaf cover blanketing the planet's vegetated regions was determined using satellite data from NASA's Moderate Resolution Imaging Spectrometer and the National Oceanic and Atmospheric Administration's Advanced Very High Resolution Radiometer instruments.
Carbon dioxide as a plant fertilizer
Previous research suggests that carbon dioxide boosts photosynthesis in plants, and in turn facilitates plant growth.
"Green leaves use energy from sunlight through photosynthesis to chemically combine carbon dioxide drawn in from the air with water and nutrients tapped from the ground to produce sugars, which are the main source of food, fiber and fuel for life on Earth," according to Science Daily.
Scientists believe carbon dioxide fertilization is the most important factor for increasing plant growth, as it has contributed to 70 percent of the greening effect.
But there are other factors, too, say researchers, including "nitrogen, land cover change and climate change by way of global temperature, precipitation and sunlight." Together, these have vastly expanded leaf cover on Earth.
Computerized models suggest that nitrogen is the second most critical factor for plant growth."The second most important driver is nitrogen, at 9 percent. So we see what an outsized role CO2 plays in this process," said study co-author Ranga Myneni, a professor in the Department of Earth and Environment at Boston University.
Zaichun Zhu, the study's lead author, says the greening effect we're observing "has the ability to fundamentally change the cycling of water and carbon in the climate system." Zhu performed the first half of the study alongside Myneni as a visiting researcher at Boston University.
An international team of scientists worked on the study, employing 32 authors from 24 institutions across eight countries.
Green leaves cover 32 percent of Earth's surface
"About 85 percent of Earth's ice-free lands is covered by vegetation. The area covered by all the green leaves on Earth is equal to, on average, 32 percent of Earth's total surface area -- oceans, lands and permanent ice sheets combined," reports Science Daily.
"While rising carbon dioxide concentrations in the air can be beneficial for plants, it is also the chief culprit of climate change. The gas, which traps heat in Earth's atmosphere, has been increasing since the industrial age due to the burning of oil, gas, coal and wood for energy and is continuing to reach concentrations not seen in at least 500,000 years. The impacts of climate change include global warming, rising sea levels, melting glaciers and sea ice as well as more severe weather events."
Another one of the study's co-authors, Dr. Philippe Ciais, says it's important to understand that the benefits carbon dioxide is having on plant life may be limited. "Studies have shown that plants acclimatize, or adjust, to rising carbon dioxide concentration and the fertilization effect diminishes over time," said Ciais, associate director of the Laboratory of Climate and Environmental Sciences, Gif-suv-Yvette, France.
In conclusion, scientists remind us that the predictions are not entirely certain. "While the detection of greening is based on data, the attribution to various drivers is based on models," said co-author Josep Canadell of the Oceans and Atmosphere Division in the Commonwealth Scientific and Industrial Research Organisation in Canberra, Australia.
He added that while their models do theorize the "best possible simulation of Earth system components," there is still room for improvement.
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